Coulomb dipole strength distribution of neutron-rich carbon isotopes

초록

We investigate the Coulomb dipole excitation (CDE) of neutron-rich carbon isotopes, focusing on 15${<}^{>}15$C and 19${<}^{>}19$C, which consist of a core nucleus and one valence neutron. The Coulomb dipole strength distribution dB(E1)/dEx$dB(E1)/d{E}_{\text{x}}$ is extracted from experimental Coulomb dissociation cross sections using both general and relativistic calculations of virtual photon numbers. Despite similar beam energies, the dissociation cross section of 19${<}^{>}19$C + Pb is significantly larger than that of 15${<}^{>}15$C + Pb, reflecting their difference in neutron separation energy. We also compute theoretical strength distributions using a simple model involving the spectroscopic factor S and the potential radius r0$r_0$, achieving good agreement with the experimental data. The extracted parameters (S, r0$r_0$) are reasonable within physical expectations. This study confirms the importance of low neutron separation energy in enhancing Coulomb breakup reaction and provides a useful framework for understanding dipole excitation mechanisms in weakly bound neutron-rich nuclei. In particular, the Coulomb dipole excitation (CDE) potential, which incorporates the Coulomb dipole strength distribution, plays a crucial role in describing the Coulomb breakup of weakly bound neutron-rich nuclei.

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